A thermal engine that starts after lunch

From late May to mid-September the weather around Corfu is driven by the sun, not by the fronts you know from northern Europe. The land heats up faster than the sea, air rises over the mainland and the islands, and cooler air is drawn in from the sea to replace it. The result is the Maistro: a north-westerly that fills in around 13:00, peaks between 15:00 and 17:00 at 12–20 knots, and dies with the sun.

This is why we tell crews to leave early and arrive early. A morning passage under engine or in a light breeze, an afternoon of real sailing, and the hook down or lines ashore by 17:00, before the gusts and before the best spots fill up.

Where the wind bends

The Corfu channel. Between the island and the Albanian and Greek mainland the Maistro is funnelled and turns to follow the channel. Expect it to run more northerly north of Corfu town and to accelerate off Kassiopi and the Pantokrator massif, where afternoon gusts of 25 knots are common on a day the open-sea forecast says 15.

The south channel and Paxos. Open to the north-west, so the afternoon sea and swell build on the crossing to Paxos. Leave Gouvia by 09:00 and you cross flat water; leave at 13:00 and you beat into a short chop.

Nights and katabatics. On clear nights the mountains of Corfu and Albania drain cold air downhill. Anchorages under high ground on the north-east coast (Agios Stefanos, Kouloura, Kalami) can get sudden gusts from the land at 02:00. Set the anchor for that, not for the breeze you anchored in.

Spring and autumn are different

April, May and October are the months with real weather. Atlantic and Mediterranean lows still pass, bringing a day or two of southerly wind, rain and swell, then clear north-westerlies behind the front. Late August and September add the first thunderstorms as the still-warm sea meets cooler air aloft; they come through fast, usually in the afternoon or at night, with squalls of 30–40 knots that last twenty minutes. Corfu is the wettest island in Greece, with roughly 1,100 mm of rain a year, but almost all of it falls between October and April.

Long-term averages for Corfu, rounded. Rain days are days with at least 1 mm.

Deep water, named winds, short seas

The Ionian is the basin between the heel of Italy, Sicily and the west coast of Greece. It is the deepest part of the Mediterranean (the Calypso Deep, south-west of Pylos, reaches 5,267 m), so there are no tides to speak of, no tidal streams, and the sea state is made entirely by the wind. Seas are short and steep rather than long and rolling. A force 6 here is wetter work than a force 6 on an Atlantic swell, but it also lies down within hours of the wind dropping.

Along the Greek side the islands shelter each other. The chain from Corfu down through Paxos, Lefkada, Meganisi, Ithaca, Kefalonia and Zakynthos leaves a strip of mostly protected water inside it, which is what makes the Ionian such a good bareboat ground. Outside the chain, on the west-facing coasts, the open-sea swell arrives unhindered: that is the side to avoid when a westerly or southerly is blowing.

The winds, by their old names

Greek sailors, and most Mediterranean forecasts, still name winds by direction. Learn these eight and the VHF bulletin makes sense.

Local effects worth knowing further south

Lefkada canal and the inland sea. The water between Lefkada, the mainland and Meganisi is almost a lake, but the Maistro accelerates through the gap between Lefkada and Meganisi and down the Meganisi channel: 25–30 knots in the channel on a 15-knot day.

Kefalonia and Ithaca. Steep, high islands. Expect the wind to go round the ends in strength and to fall calm or gust down the lee slopes. The Ithaca channel is a wind tunnel in a northerly.

Thunderstorms. From late August the afternoons over the mainland mountains build towering cumulus. If the tops go flat and spread, and the air goes still and heavy, a squall is coming off the land. Drop the sails before it arrives, not during.

Our weather is made over Sicily, Malta and Libya

Weather systems in the Mediterranean move from west to east. For the Ionian the breeding ground is the central basin to our south-west: the Tyrrhenian, the Strait of Sicily, the Malta channel and the Gulf of Sirte off Libya. A low that forms off Tunisia on a Monday is on top of Kefalonia by Wednesday. What Malta is getting today is a fair preview of our Thursday.

Three things happen there that matter to us.

Cyclogenesis. Cold air from Europe spilling south over a warm sea produces lows, most often in the Gulf of Genoa and over the Sicily channel. In spring and autumn these are the systems that bring the Sirocco then Garbis sequence described above. In late autumn and winter, when the sea is still warm and the upper air is cold, one of them can turn into a Medicane.

The Sirocco and the dust. A low to the west pulls Saharan air north across Libya and Tunisia. It arrives here warm, hazy and often carrying dust: the sky turns milky, visibility drops to a few miles, and rain leaves red mud on the deck. Dust days are usually followed by a southerly blow and then a front.

Swell from the open sea. A gale between Sicily and Crete sends a long south-westerly swell into the Ionian a day before the wind itself, and it runs into every bay that faces south or west. A calm morning with a long swell rolling into Paxos is a reason to look at the synoptic chart, not to relax.

For a seven-day charter this means: check the whole central Mediterranean on the day you arrive, not only Corfu. If there is a deepening low near Sicily, build your week around it. Go north and east into the shelter of the channel while it passes, and save the Paxos and open-water days for the clear north-westerlies that follow.

The one weather event that changes the plan

A Medicane, a Mediterranean hurricane, is a small tropical-like cyclone that forms over the sea when the water is still warm in late autumn and cold air arrives high above it. It brings hurricane-force gusts, torrential rain and a storm surge, and it can sit over the islands for a day or more instead of passing through in an hour.

They are rare, perhaps one or two a year across the whole Mediterranean, and most of them stay at sea or weaken before landfall. But the Ionian is one of the two places where they form and travel, the other being the sea between Sicily and Libya, and September to November is the season. That is still charter season for us. We do not cancel the season for them; we watch for them.

The ones that matter here

If one is forecast during your charter

We watch the models daily from mid-August. When a Medicane is possible during your dates, this is what happens.

1. We call you. Not an email: a call, at the number on your booking, as soon as a track is credible, usually three to five days out.
2. You move to a safe berth, at our cost, or we move the boat for you. Gouvia, Lefkada and Preveza are the usual harbours; we choose the one the track misses.
3. We will change your itinerary, shorten it or delay the start. Weather is a legitimate reason to amend a charter and we do not charge for it.
4. If the storm arrives anyway, stay aboard and stay in the marina. Do not take a car, do not go sightseeing, do not move the boat. A yacht in a marina with doubled lines is the safest place you can be.

Ianos in 2020 is the benchmark. Boats that were in sheltered marinas with proper lines came through; boats left on exposed moorings or anchored in open bays did not. If we ask you to move, it is because of that.

Where to look before you leave the pontoon

Windy is the tool we recommend to guests: set it to the ECMWF or ICON model, look at the whole Mediterranean rather than the zoomed-in Corfu view, and check the gusts layer as well as the mean wind.

Change the model in the menu to ICON or ECMWF and watch the 10-day trend, not a single run.

How to read the numbers

Greek forecasts use the Beaufort scale. The knots are the mean wind; gusts in a squall or a channel can be half as strong again. If a forecast offers force 6 or more on the day you planned to cross to Paxos, cross another day.